[BUG]: Python 3.14.0a3 test failure: test_roundtrip_with_dict: AttributeError: 'pybind11_tests.pickling.PickleableWithDict' object has no attribute 'dynamic' + test_dynamic_attributes

[befeleme]

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What version (or hash if on master) of pybind11 are you using?

2.13.6

Problem description

I attempt to build pybind11 2.13.6 with Python 3.14.0a3 for Fedora Linux, the 3 tests have started to fail since a3.

What's new in Python 3.14 states:

Set the default protocol version on the pickle module to 5. For more details, see pickle protocols.

___________________________ test_dynamic_attributes ____________________________

    @pytest.mark.xfail("env.PYPY")
    def test_dynamic_attributes():
        instance = m.DynamicClass()
        assert not hasattr(instance, "foo")
        assert "foo" not in dir(instance)
    
        # Dynamically add attribute
        instance.foo = 42
        assert hasattr(instance, "foo")
        assert instance.foo == 42
        assert "foo" in dir(instance)
    
        # __dict__ should be accessible and replaceable
        assert "foo" in instance.__dict__
        instance.__dict__ = {"bar": True}
>       assert not hasattr(instance, "foo")
E       AssertionError: assert not True
E        +  where True = hasattr(<pybind11_tests.methods_and_attributes.DynamicClass object at 0x7f7c18238330>, 'foo')

instance   = <pybind11_tests.methods_and_attributes.DynamicClass object at 0x7f7c18238330>

../../tests/test_methods_and_attributes.py:312: AssertionError
----------------------------- Captured stdout call -----------------------------
### test_submodule_methods_and_attributes(module_&)::DynamicClass @ 0x5588e466d1b0 created via default constructor
_________________ test_roundtrip_with_dict[PickleableWithDict] _________________

cls_name = 'PickleableWithDict'

    @pytest.mark.xfail("env.PYPY")
    @pytest.mark.parametrize("cls_name", ["PickleableWithDict", "PickleableWithDictNew"])
    def test_roundtrip_with_dict(cls_name):
        cls = getattr(m, cls_name)
        p = cls("test_value")
        p.extra = 15
        p.dynamic = "Attribute"
    
        data = pickle.dumps(p, pickle.HIGHEST_PROTOCOL)
        p2 = pickle.loads(data)
        assert p2.value == p.value
        assert p2.extra == p.extra
>       assert p2.dynamic == p.dynamic
E       AttributeError: 'pybind11_tests.pickling.PickleableWithDict' object has no attribute 'dynamic'

cls        = <class 'pybind11_tests.pickling.PickleableWithDict'>
cls_name   = 'PickleableWithDict'
data       = b'\x80\x05\x95`\x00\x00\x00\x00\x00\x00\x00\x8c\x17pybind11_tests.pickling\x94\x8c\x12PickleableWithDict\x94\x93\x94)\x81\x94\x8c\ntest_value\x94K\x0f}\x94\x8c\x07dynamic\x94\x8c\tAttribute\x94s\x87\x94b.'
p          = <pybind11_tests.pickling.PickleableWithDict object at 0x7f7c182395e0>
p2         = <pybind11_tests.pickling.PickleableWithDict object at 0x7f7c18239470>

../../tests/test_pickling.py:52: AttributeError
_______________ test_roundtrip_with_dict[PickleableWithDictNew] ________________

cls_name = 'PickleableWithDictNew'

    @pytest.mark.xfail("env.PYPY")
    @pytest.mark.parametrize("cls_name", ["PickleableWithDict", "PickleableWithDictNew"])
    def test_roundtrip_with_dict(cls_name):
        cls = getattr(m, cls_name)
        p = cls("test_value")
        p.extra = 15
        p.dynamic = "Attribute"
    
        data = pickle.dumps(p, pickle.HIGHEST_PROTOCOL)
        p2 = pickle.loads(data)
        assert p2.value == p.value
        assert p2.extra == p.extra
>       assert p2.dynamic == p.dynamic
E       AttributeError: 'pybind11_tests.pickling.PickleableWithDictNew' object has no attribute 'dynamic'

cls        = <class 'pybind11_tests.pickling.PickleableWithDictNew'>
cls_name   = 'PickleableWithDictNew'
data       = b'\x80\x05\x95c\x00\x00\x00\x00\x00\x00\x00\x8c\x17pybind11_tests.pickling\x94\x8c\x15PickleableWithDictNew\x94\x93\x94)\x81\x94\x8c\ntest_value\x94K\x0f}\x94\x8c\x07dynamic\x94\x8c\tAttribute\x94s\x87\x94b.'
p          = <pybind11_tests.pickling.PickleableWithDictNew object at 0x7f7c18239750>
p2         = <pybind11_tests.pickling.PickleableWithDictNew object at 0x7f7c182398c0>

Reproducible example code

Is this a regression? Put the last known working version here if it is.

Not a regression

[henryiii]

🤖 AI text below 🤖

This was verified against current master. Pickling with __dict__ works on Python 3.14; the fixes landed in #5646, #5658, and #5697. All three failing assertions from this report now pass on Python 3.14.6.

If you can still reproduce this with current master (v3), please comment and we can reopen.